Test ID: IODCU    
Iodine/Creatinine Ratio, Random, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Assessment of iodine toxicity or recent iodine exposure in a random urine collection


Monitoring iodine excretion rate as index of replacement therapy

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Iodine is an essential element for thyroid hormone production.


The measurement of urinary iodine is preferred for assessment of toxicity, recent exposure, and monitoring iodine excretion rate as an index of replacement therapy.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

0-17 years: not established

> or =18 years: <584 mcg/g creatinine

Interpretation Provides information to assist in interpretation of the test results

Measurement of urinary iodine excretion provides the best index of dietary iodine intake and deficiency is generally indicated when the concentrations are below 100 mcg/L. For deficiency, 10 repeat random urines are recommended.


World Healthcare Organization (WHO) Criteria for Assessing Iodine Status(1)


Children older than 6 years and adults

Median urinary iodine (mcg/L)

Iodine intake

Iodine status



Severe deficiency



Moderate deficiency



Mild deficiency



Adequate nutrition


Above requirements

May pose a slight risk of more than adequate



Risk of adverse health consequences


Pregnant women

Median urinary iodine (mcg/L)

Iodine intake






Above requirements




Lactating women and children younger than 2 years

Median urinary iodine (mcg/L)

Iodine intake





Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Rifai, N, Horwath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018

2. Knudsen N, Christiansen E, Brandt-Christensen M, Nygaard B, Perrild H: Age- and sex-adjusted iodine/creatinine ratio. A new standard in epidemiological surveys? Evaluation of three different estimates of iodine excretion based on casual urine samples and comparison to 24 h values. Eur J Clin Nutr. 2000 Apr;54(4):361-363

3. Liberman CS, Pino SC, Fang SL, Braverman LE, Emerson CH: Circulating iodine concentrations during and after pregnancy. J Clin Endocrinol Metab. 1998 Oct;83(10):3545-3549

4. Pfeiffer CM, Sternberg MR, Schleicher RL, Haynes BMH, Rybak ME, Pirkle JL: CDC's Second National Report on Biochemical Indicators of Diet and Nutrition in the US Population is a valuable tool for researchers and policy makers. J Nutr. 2013 Jun;143(6):938S-947S

5. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry: Toxicological Profile for Iodine. HHS; 2004. Accessed November 25, 2020. Available at www.atsdr.cdc.gov/ToxProfiles/tp158.pdf

6. Leung AM, Braverman LE: Consequences of excess iodine. Nat Rev Endocrinol. 2014 Mar;10(3):136-142. doi: 10.1038/nrendo.2013.251

Special Instructions Library of PDFs including pertinent information and forms related to the test